Conventional wireless networks are designed to prevent transmissions between the different nodes from interfering one with the others, for example by including techniques using reservation of wireless channels by time division or frequency division.
Transmissions in such systems can be, for example, performed using digital network coding (DNC) to increase capacity. An example use of DNC is shown in FIG. 1a and FIG. 1b, where two nodes A and B willing to exchange signals using DNC transmit sequentially signals a(t) and b(t), under the form of digital packets a and b, to a router node R. After having completely received packets a and b, the router node mixes the content of the packets, for example by linear combination, and broadcasts to destination devices a digital signal, corresponding to the algebraic combination a+b.
It has been noticed that these networks present major drawbacks in terms of transmission capacity, since signals a and b have to be transmitted sequentially. Solutions have thus been proposed, using interferences of analog signals to allow concurrent transmissions. Accordingly, it has been recently proposed to use the analog counterpart of DNC, which is the analog network coding (ANC). An exemplary use of such coding can be seen in FIG. 1c, where nodes A and B simultaneously transmit packets to the router node R, under the form of analog signals Data[a](t) and Data[b](t). Signals mix naturally over the wireless channel, due to interference, and thus the router node R receives a mixed signal MData[a,b](t), which is then forwarded to the destination nodes without the contained packets being decoded or recovered at the router node. Then, destination nodes that are aware of the mixing process can successfully recover the desired packets.
However, in existing systems carrying out analog network coding, major drawbacks have appeared, namely in terms of feedback and acknowledgment of the transmissions. Indeed, in known systems, destination nodes can not determine, before receiving an interfered signal, whether they are, or not, able to decode such a signal. Moreover, there is no mechanism for the router node and the transmitting nodes to know whether decoding has been successfully performed, and thus whether transmission has been fully completed.